Writing line in file via Dockerfile

Product support balenaOS
1

Hello,

I’m trying to add a line in a file via Docker file for setting up can settings. To do this I used the following command “echo” in dockerfile see: docker - Editing Files from dockerfile - Stack Overflow. But when I reach this file via ssh I can’t see the line that I add. Can someone help me with it ?
Dockerfile:

dockerfile
dockerfile791×455 16.9 KB

Ssh:
ssh
ssh2556×890 131 KB

Building:
building
building1164×1008 65.8 KB

2

Hi @hugo,

You cannot modify the /etc/hosts file during the image build, since the hosts file is maintained by docker on container startup. docker-compose does support the extra_hosts field which you can use to define the extra hosts you want, see: docker-compose.yml fields - Balena Documentation and Compose file version 2 reference | Docker Documentation

From the docker-compose docs, something like the following:

extra_hosts:
  - "somehost:162.242.195.82"
  - "otherhost:50.31.209.229"

Let us know how this works for you!

Regards,
Christina

4

Hi, following up per my colleague’s previous message. As she said, you cannot modify the /etc/hosts file during the image build since the hosts file is maintained by docker on container startup, but docker-compose does support the extra_hosts field which you can use to define the extra hosts you want. Could you please confirm whether this works for you?

6

Hi, yes it is thank you for your help !